A variable is an identifier that refers to the data item stored at a particular memory location. This data item can be accessed in the program simply by using the variable name. The value of a variable can be changed by assigning different values to it at various places in a program.

Constants refer to fixed values that the program may not alter. Constants can be of any of the basic data types. The way each constant is represented depends upon its type. Constants are also called literals.

Every word in C++ language is a keyword or an identifier. Keywords in C++ language cannot be used as a variable name. They are specifically used by the compiler for its own purpose and they serve as building blocks of a C++ program. C++ language has some reserve words which are called keywords of C++ language. These are the part of the C++ Tokens.

Character set is the combination of English language (Alphabets and White spaces) and math's symbols (Digits and Special symbols). Character Set means that the characters and symbols that a C++ Program can understand and accept. These are grouped to form the commands, expressions, words, c-statements and other tokens for C++ Language.

A Program is a set of Instructions and a Programmer is that who develops the program .For creating a program a programmer must use a language called as the programming language So generally a programming language is used for creating the software’s.

As we know that Software is a Program. And a Program is that which Contains set of instructions, and an Instruction contains Some Tokens. So Tokens are used for Writing the Programs the various Types of Tokens those are contained by the Programs.